#pragma once

#include <future>
#include <utility>

namespace mbgl {

// A movable type-erasing function wrapper. This allows to store arbitrary
// invokable things (like std::function<>, or the result of a movable-only
// std::bind()) in the queue. Source: http://stackoverflow.com/a/29642072/331379
class Message {
public:
    virtual ~Message() = default;
    virtual void operator()() = 0;
};

template <class Object, class MemberFn, class ArgsTuple>
class MessageImpl : public Message {
public:
    MessageImpl(Object& object_, MemberFn memberFn_, ArgsTuple argsTuple_)
        : object(object_),
          memberFn(memberFn_),
          argsTuple(std::move(argsTuple_)) {}

    void operator()() override { invoke(std::make_index_sequence<std::tuple_size_v<ArgsTuple>>()); }

    template <std::size_t... I>
    void invoke(std::index_sequence<I...>) {
        (object.*memberFn)(std::move(std::get<I>(argsTuple))...);
    }

    Object& object;
    MemberFn memberFn;
    ArgsTuple argsTuple;
};

template <class ResultType, class Object, class MemberFn, class ArgsTuple>
class AskMessageImpl : public Message {
public:
    AskMessageImpl(std::promise<ResultType> promise_, Object& object_, MemberFn memberFn_, ArgsTuple argsTuple_)
        : object(object_),
          memberFn(memberFn_),
          argsTuple(std::move(argsTuple_)),
          promise(std::move(promise_)) {}

    void operator()() override { promise.set_value(ask(std::make_index_sequence<std::tuple_size_v<ArgsTuple>>())); }

    template <std::size_t... I>
    ResultType ask(std::index_sequence<I...>) {
        return (object.*memberFn)(std::move(std::get<I>(argsTuple))...);
    }

    Object& object;
    MemberFn memberFn;
    ArgsTuple argsTuple;
    std::promise<ResultType> promise;
};

template <class Object, class MemberFn, class ArgsTuple>
class AskMessageImpl<void, Object, MemberFn, ArgsTuple> : public Message {
public:
    AskMessageImpl(std::promise<void> promise_, Object& object_, MemberFn memberFn_, ArgsTuple argsTuple_)
        : object(object_),
          memberFn(memberFn_),
          argsTuple(std::move(argsTuple_)),
          promise(std::move(promise_)) {}

    void operator()() override {
        ask(std::make_index_sequence<std::tuple_size_v<ArgsTuple>>());
        promise.set_value();
    }

    template <std::size_t... I>
    void ask(std::index_sequence<I...>) {
        (object.*memberFn)(std::move(std::get<I>(argsTuple))...);
    }

    Object& object;
    MemberFn memberFn;
    ArgsTuple argsTuple;
    std::promise<void> promise;
};

namespace actor {

template <class Object, class MemberFn, class... Args>
std::unique_ptr<Message> makeMessage(Object& object, MemberFn memberFn, Args&&... args) {
    auto tuple = std::make_tuple(std::forward<Args>(args)...);
    return std::make_unique<MessageImpl<Object, MemberFn, decltype(tuple)>>(object, memberFn, std::move(tuple));
}

template <class ResultType, class Object, class MemberFn, class... Args>
std::unique_ptr<Message> makeMessage(std::promise<ResultType>&& promise,
                                     Object& object,
                                     MemberFn memberFn,
                                     Args&&... args) {
    auto tuple = std::make_tuple(std::forward<Args>(args)...);
    return std::make_unique<AskMessageImpl<ResultType, Object, MemberFn, decltype(tuple)>>(
        std::move(promise), object, memberFn, std::move(tuple));
}

} // namespace actor
} // namespace mbgl
